<html lang="en">

<meta charset="utf-8">

<title>Java 8: A quick overview over the good parts - Writing Java has never been so fun</title>

<meta name="description" content="Java 8: A quick overview over the good parts">

<meta name="author" content="Benjamin Schmid | @bentolor">

<meta name="apple-mobile-web-app-capable" content="yes"/>

<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent"/>

<link href='http://fonts.googleapis.com/css?family=Lato:400,700,400italic,700italic' rel='stylesheet' type='text/css'>

<link rel="stylesheet" href="css/reveal.css">

<link rel="stylesheet" href="css/theme/lt.css" id="theme">

<!-- For syntax highlighting -->

<link rel="stylesheet" href="lib/css/zenburn.css">

<!-- If the query includes 'print-pdf', use the PDF print sheet -->

<script>

document.write('<link rel="stylesheet" href="css/print/' + ( window.location.search.match(/print-pdf/gi) ? 'pdf' : 'paper' ) + '.css" type="text/css" media="print">');

</script>

<!--[if lt IE 9]>

<div class="reveal">

<div class="slides">

<h1 style="margin: 50px 0 .3em">Java 8<br/>The good parts</h1>

<h3 style="font-size:1.2em;margin-bottom:2em">Writing Java has never been so fun</h3>

<p style="text-align: right">

<a href="https://twitter.com/bentolor">@bentolor</a>

</p>

<h2>Table of contents</h2>

<p style="font-size: 76%; text-align: center; color: #666; margin: -1.5em 0 1em 0">Usage hint: Use mouse scoll or cursor right &amp; <strong>down</strong> to navigate!</p>

<div id="table-of-contents"></div>

<section class="glow">

<section>

<h2 class="slide-header">Java 8 is <em>big</em></h2>

<h5>Language</h5>

<ul>

<li>Lambdas &amp; Functional Interfaces</li>

<li>Method References</li>

<li>Default Methods</li>

<li>Better annotations</li>

<li>Better Type Inference</li>

</ul>

</section>

<section>

<h2>Java 8 is <em>big</em></h2>

<h5>Runtime library</h5>

<ul>

<li>Streams</li>

<li>Optional</li>

<li>Multicore Support (Parallel)</li>

<li>Native Javascript</li>

<li>Many Goodies</li>

</ul>

</section>

<section>

<h2>Java 8 is <em>big</em></h2>

<h5>Compiler &amp; Tools</h5>

<ul>

<li>Reflection: Parameter names</li>

<li>CLI: jjs (Nashorn)</li>

<li>CLI: jdeps</li>

<li>Death of PermGen</li>

</ul>

</section>

<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Language changes</h2>

<section>

<h2 class="slide-header">Lambdas</h2>

<p>Basic form</p>

<pre><code class="java">(params) -> expression

(params) -> statement

(params) -> { statements }</code></pre>

<p class="tgap">A simple example (no parameters):</p>

<pre><code class="java">Runnable r = () -> System.out.println("Hello!");

r.run();</code></pre>

<p class="tgap">Example with parameter (Type inferred!)<p>

<pre><code class="java">Arrays.asList( "a", "b", "d" ).forEach( e -> System.out.println( e ) );</code></pre>

</section>

<section>

<h2>Lambdas</h2>

<p>Lambdas can access outer field / variables if they are <em>(effectively)</em> final</p>

<pre><code class="java">String separator = ",";

Arrays.asList( "a", "b", "d" )

.forEach( (String e) -> System.out.print(e+separator) );

//separator = ";" // would break!</code></pre>

<p class="tgap">Lambdas may return values (inline/explicit)</p>

<pre><code class="java">Arrays.asList( "a", "b", "d" ).sort( ( e1, e2 ) -> e1.compareTo( e2 ) );

// or:

Arrays.asList( "a", "b", "d" ).sort( ( e1, e2 ) -> {

return e1.compareTo( e2 );

} ); </code></pre>

</section>

<section>

<h2 class="slide-header">Functional interfaces</h2>

<pre><code class="java">Comparator &lt;Apple&gt; c =

(Apple a1, Apple a2) -> a1.getWeight().compareTo(a2.getWeight());</code></pre>

<h5 class="fragment tgap">Wait, wait, wait... Comparator? How does this work?</h5>

<pre class="fragment"><code class="java">@FunctionalInterface

public interface Comparator&lt;T&gt; {

int compare(T o1, T o2);

}</code></pre>

</section>

<section>

<h2><code>@FunctionalInterface</code></h2>

<p> Conceptually, a functional interface has exactly <strong>one abstract

method.</strong> As such, it may be implicitly converted to a lambda expression.</p>

<p>Note that <strong>instances of functional interfaces</strong> can be created with

<em>lambda expressions</em> or method/constructor references. </p>

<p><strong>But:</strong> To avoid breakage by accidently adding further methods , these

interfaces <strong><u>should</u></strong> be explicitly tagged with <code>@FunctionalInterface</code>.

</p>

</section>

<section>

<h2 class="slide-header">Interface <code>default</code> methods</h2>

<p>In Java 8 you can write:</p>

<pre><code class="java">List&lt;Integer&gt; numbers = Arrays.asList(3, 5, 1, 2, 6);

numbers.sort(Comparator.naturalOrder());</code></pre>

<p class="tgap fragment">Huh? <code>java..util.List</code> now requires a <code>sort()</code>-Method?<br/>Will all of my code break now?</p>

<pre class="fragment"><code class="java">public interface List&lt;E&gt; extends Collection&ltE&gt; {

// ...

default void sort(Comparator&lt;? super E&gt; c) {

// ...

}

}</code></pre>

</section>

<section>

<h2 class="slide-header">Interface <code>static</code> methods</h2>

<pre><code class="java">private interface PersonFactory {

// Interfaces now allow static methods

static Person createPerson( String firstname, String lastname ) {

return new Person(firstname, lastname);

}

}</code></pre>

</section>

<section>

<h2 class="slide-header">Method references</h2>

<p>Given the following interface</p>

<pre><code class="java mb-30">public interface MyFormatter&lt;T&gt; {

String format(T object);

}

public &lt;T&gt; String format(T o, MyFormatter&lt;T&gt; formatter) {

return formatter.format(o);

}</code></pre>

<div class="fragment tgap">

<p>We can simply reuse existing other implementations</p>

<pre><code class="java">format(32, Integer::toHexString)</code></pre>

</div>

</section>

<section>

<h2 >Supported method references</h2>

<ul>

<li><strong>static method:</strong> <code>Class::staticMethodName</code></li>

<li><strong>instance method of a <em>particular</em> object</strong> <code>object::methodName</code></li>

<li><strong>instance method of an <em>arbitrary</em> object</strong> <code>Type::methodName</code></li>

<li><strong>constructor:</strong> <code>ClassName::new</code></li>

</ul>

</section>

<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Runtime library enhancement</h2>

<section>

<h2 class="slide-header">Streams</h2>

<pre><code class="java mb-30">Collection&lt;Task&gt; tasks = getTasks();

long totalPointsOfOpenTasks = tasks

.stream()

.filter( task -> task.getStatus() == Status.OPEN )

.mapToInt( Task::getPoints )

.sum();

System.out.println( "Total points: " + totalPointsOfOpenTasks );</code></pre>

</section>

<section>

<h2 class="slide-header">Stream operations</h2>

<h4>Are divided into</h4>

<ul class="mb-30">

<li><em>Intermediate operations</em> (returning another <code>Stream&lt;T&gt;</code>)</li>

<li><em>Terminal operations</em> (returning the final result)</li>

</ul>

<h4>Parallel processing</h4>

<p>Out-of-the box support of parallel processing (Multi-threading!)</p>

<p><pre><code>stream.parallel()</code></pre></p>

</section>

<section>

<h2 class="slide-header">Complex stream example</h2>

<pre><code class="java mb-30">// Calculate the weight of each tasks (as percent of total points)

final Collection&lt;String&gt; result = tasks

.stream() // Stream&lt;String&gt;

.mapToInt( Task::getPoints ) // IntStream

.asLongStream() // LongStream

.mapToDouble( points -> points / totalPoints ) // DoubleStream

.boxed() // Stream&lt;Double&gt;

.mapToLong( weigth -> ( long )( weigth * 100 ) ) // LongStream

.mapToObj( percentage -> percentage + "%" ) // Stream&lt;String&gt;

.collect( Collectors.toList() ); // List&lt;String&gt;

System.out.println( result );</code></pre>

</section>

<h2 class="slide-header">Optional</h2>

<p>Allows you to commit to a non-<code>null</code> convention in your project

<br/> &amp; offers some convenience. </p>

<pre><code class="java mb-30">Optional&lt;String&gt; fullName = Optional.ofNullable( null );</code></pre>

<pre><code class="java mb-30">log.info( "Full Name is set? " + fullName.isPresent() );

log.info( "Full Name: " + fullName.orElseGet( () -> "[none]" ) );

log.info( fullName.map( s -> "Hey " + s + "!" ).orElse( "Hey Stranger!" ) );</code></pre>

<p>No more <code>NullPointerException</code>?</p>

<h2 class="slide-header">Native Javascript Support (Nashorn)</h2>

<h5>Use / Run Javascript in your code:</h5>

<pre><code class="java mb-30">ScriptEngineManager manager = new ScriptEngineManager();

ScriptEngine engine = manager.getEngineByName( "JavaScript" );

System.out.println( engine.eval( "function f() { return 1; }; f() + 1;" ) );</code></pre>

<h5>From command line</h5>

<pre><code class="mb-30">jjs server.js</code></pre>

<section>

<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Smaller goodies</h2>

</section>

<section>

<h2 class="slide-header">Better Annotations</h2>

<h5>Repeatable</h5>

<pre><code class="java mb-30">@Filter( "filter1" )

@Filter( "filter2" )

public interface Filterable { }</code></pre>

<h5>... assigned to variables, constructors, maps, casts, ...</h5>

<pre><code class="java mb-30">@NotNull String myString = "Foo"

new @Interned MyObject()

myString = (@NonNull String) myObject;</code></pre>

<h5>... used in Generics</h5>

<pre><code class="java mb-30">List<@Email String> emails = ...</code></pre>

<h5>... and more!</h5>

</section>

<section>

<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Better type inference</h2>

</section>

<section>

<h2 class="slide-header">Parameter names</h2>

<pre><code class="java mb-30">Method method = ParameterNames.class.getMethod( "main", String[].class );

for( final Parameter parameter: method.getParameters() ) {

System.out.println( "Parameter: " + parameter.getName() );

}</code></pre>

</section>

<section>

<h2 class="slide-header"> Date/Time API (JSR 310)</h2>

<ul>

<li>More convenience & easier operations. </li>

<li>Time-zone less data types (i.e. <code>LocalDate</code>) </li>

</ul>

</section>

<section>

<h2 class="slide-header"><code>java.util.Base64</code></h2>

</section>

<section>

<h2 class="slide-header">Better Multithreading support</h2>

<ul>

<li><code>list.parallelStream()</code></li>

<li><code>stream.parallel()</code></li>

<li><code>ConcurrentMap.parallelStream()</code></li>

<li><code>Arrays.parallelSort()</code></li>

<li><code>Arrays.parallelSetAll()</code></li>

</ul>

</section>

<section>

<h2 class="slide-header">Small enhancements in <code>java.util.concurrent</code></h2>

</section>

<section>

<h2 class="slide-header" style="font-size:3em;margin-top: 50px">Tools & JVM</h2>

</section>

<section>

<h2 class="slide-header">jdeps</h2>

<p>Class dependency analyzer</p>

<pre><code class="mb-30">$ jdeps org.springframework.core-3.0.5.jar

org.springframework.core-3.0.5.jar -> lib\rt.jar

org.springframework.core (org.springframework.core-3.0.5.jar)

-> java.io

-> java.lang

-> java.lang.annotation

-> java.lang.ref

-> java.lang.reflect

-> java.util

-> java.util.concurrent

-> org.apache.commons.logging not found

-> org.springframework.asm not found

org.springframework.core.annotation (org.springframework.core-3.0.5.jar)

-> java.lang

-> java.lang.annotation

-> java.lang.reflect

-> java.util</code></pre>

</section>

<section>

<h2 class="slide-header">PermGen is now <br/><a href="http://www.javacodegeeks.com/2013/02/java-8-from-permgen-to-metaspace.html">MetaSpace</a></h2>

</section>

<h2 class="slide-header">Resources</h2>

<ul>

<li><a href="http://www.javacodegeeks.com/2014/05/java-8-features-tutorial.html#new_java_tools">Java 8 Features – The ULTIMATE Guide</a></li>

<li><a href="http://java.dzone.com/articles/whats-wrong-java-8-part-vi">Whats wrong with Java 8</a></li>

<li><a href="http://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html#StreamOps">Streams API</a></li>

<li><a href="https://github.com/java8/Java8InAction/">Java 8 in Action</a></li>

</ul>

<h3 style="font-size:3em;margin-top:30px;margin-bottom:.5em">Thank you :)</h3>

<iframe src="http://ghbtns.com/github-btn.html?user=bentolor&repo=java8-lightningtalk&type=watch&count=true" allowtransparency="true" frameborder="0" scrolling="0" width="110" height="20" style="position: absolute; top: 20px; left: 20px; z-index: 9999"></iframe>

<a href="https://github.com/bentolor/java8-lightningtalk" style="position: absolute; top: 0; right: 0; z-index: 9999">

<img style="border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_red_aa0000.png" alt="Fork me on GitHub">

<script src="lib/js/head.min.js"></script>

<script src="js/reveal.min.js"></script>

// Full list of configuration options available here:

// https://github.com/hakimel/reveal.js#configuration

Reveal.initialize({

controls: true,

progress: true,

history: true,

rollingLinks: false,

slideNumber: true,

theme: Reveal.getQueryHash().theme, // available themes are in /css/theme

transition: 'linear', // default/cube/page/concave/linear(2d)

mouseWheel: true,

parallaxBackgroundImage: 'http://demo.thinkupthemes.com/spirits/wp-content/themes/Spirits/demo/images/background/background5.jpg',

parallaxBackgroundSize: '1626px 1229px', // 1229px // CSS syntax, e.g. "2100px 900px"

// Optional libraries used to extend on reveal.js

dependencies: [

{ src: 'lib/js/highlight.js', async: true, callback: function () {

window.hljs.initHighlightingOnLoad();

} },

{ src: 'lib/js/classList.js', condition: function () {

return !document.body.classList;

} },

{ src: 'lib/js/showdown.js', condition: function () {

return !!document.querySelector('[data-markdown]');

} },

{ src: 'lib/js/data-markdown.js', condition: function () {

return !!document.querySelector('[data-markdown]');

} },

{ src: 'plugin/zoom-js/zoom.js', condition: function () {

return !!document.body.classList;

} },

{ src: '/socket.io/socket.io.js', async: true, condition: function () {

return window.location.host === 'localhost:1947';

} },

{ src: 'plugin/speakernotes/client.js', async: true, condition: function () {

return window.location.host === 'localhost:1947';

} }

]

});

<script src="js/zepto.min.js"></script>

Zepto(function ($) {

var tableOfContents = $('#table-of-contents');

var tableList = $('<ol />')

$('.slide-header').each(function (index) {

var _self = $(this),

hash = '#/' + _self.closest('section').index();

tableList.append([

'<li>',

'<a href="' + hash + '">',

_self.text(),

'</a>',

'</li>'

].join(''));

});

tableOfContents.html(tableList);

});

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){

(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),

m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)

})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', 'UA-54268066-1', 'auto');

ga('send', 'pageview');